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Seven-Channel E1 Line Interface
December 2001-3
XRT5897
FEATURES D Compliant with ITU G.703 Pulse Mask Template for 2.048Mbps (E1) Rates D Seven Independent CEPT Transceivers D Supports Differential Transformer Coupled Receivers and Transmitters D On Chip Pulse Shaping for Both 75W and 120W Line Drivers D Compliant with ITU G.775 LOS Declaration/Clearing Recommendation D Optional User Selectable LOS Declaration/Clearing Delay D Compliant with ITU--T G.823 Jitter Tolerance Requirements D Logical Inputs Accept either 3.3V or 5.0V Levels D Ultra-Low Power Dissipation D +3.3V Supply Operation D Individual Transmit Channel Over Temperature Protection APPLICATIONS D SDH Multiplexer D Digital Cross Connects
GENERAL DESCRIPTION The XRT5897 is an optimized seven channel 3.3V line interface unit fabricated using low power CMOS technology. The device contains seven independent E1 channels. It is primarily targeted toward SDH multiplexers that accommodate TU12 Tributary Unit Frames. Line cards in these units multiplex 21 E1 interfaces into higher SDH rates. Devices with seven E1 interfaces such as the XRT5897 provide the most efficient method of implementing 21 channel line cards. Each channel performs the driver and receiver functions necessary to convert bipolar signals to logical levels and vice versa. The device requires transformers on both receiver and transmitter sides, and supports both balanced and unbalanced interfaces. ORDERING INFORMATION
Operating Temperature Range -40C to +75C
The device offers two distinct modes of LOS detection. The first method, which does not require an external clock, provides an LOS output indication signal with thresholds and delay that comply with the ITU G.775 requirements. In the second mode, the user provides an external clock that increases the delay for LOS declaration and clearing. This feature provides the user with the flexibility to implement LOS specifications that require a delay greater than the G.775 requirements.
Part No. XRT5897IV
Package 100 Lead TQFP (14 x 14 x 1.4mm)
Rev. 1.11
E2001
EXAR Corporation, 48720 Kato Road, Fremont, CA 94538 z (510) 668-7000 z FAX (510) 668-7017
XRT5897
BLOCK DIAGRAM
RTIP7 (69) TIP RX INPUT RING 1:2 R1 R2
Tranceiver 1 Tranceiver 2 Tranceiver 3 Tranceiver 4 Tranceiver 5 Tranceiver 6 Tranceiver 7 RXPOS7 (5) Singnal Peak Detector Receive Comparators RXNEG7 (6)
RRING7 (68) VCC LOS Detect Loss Delay Counter 1 MUX O LOS7 (4)
LOSCNT (73) LOSSEL (38) Transmit Line Drivers TIP TX OUTPUT RING 2:1 R3 9.1 R4 9.1 TRING7 (91) TTIP7 (89) Pulse Shaping
0 0 MUX 1 1
NRZ To RZ
Duty Cycle Adjust
TXCLK7 (87) TXPOS7 (85) TXNEG7 (86)
Figure 1. XRT5897 Block Diagram
Receiver Notes D The same type 1:2CT ratio transformer may be used at the receiver input and transmitter output. D R1 and R2 are both 150W for 75W operation, or 240W for 120W operation. D Return loss exceeds ITU G.703 specification with these resistors and a 1:2CT ratio input transformer. D LOSCNT (pin 73) is unconnected when LOSSEL is logic 1, or connected to an external clock when LOSSEL is logic 0. Transmitter Notes D Return loss exceeds ETSI 300 166 specification with a 1:2 ratio transformer. D R3 and R4 are always 9.1W for both 75W and 120W applications. D An approach exists that permits the user to operate the XRT5897 with a 5V power supply. For more information, please see application note TAN-12.
LOS (Loss of Signal) Notes D LOSSEL (pin 38) is connected to logic "1" for ITU G.775 compliant LOS delay, or to logic 0 for user programmable additional delay.
Rev. 1.11 2
XRT5897
PIN CONFIGURATION
LOS6 TXPOS6 TXNEG6 TXCLK6 GND TTIP6 VCC TRING6 GND TXPOS7 TXNEG7 TXCLK7 GND TTIP7 VCC TRING7 GND TRING1 VCC TTIP1 GND TXCLK1 TXNEG1 TXPOS1 LOS1
RXPOS6 RXNEG6 LOSCNT GND RTIP6 RRING6 RTIP7 RRING7 VCC GND VCC RRING5 RTIP5 GND TTIP5 VCC TRING5 GND TRING4 VCC TTIP4 GND RTIP4 RRING4 TXCLK4 75 76 51 50 TXNEG4 TXPOS4 LOS4 RXPOS4 RXNEG4 TXPOS5 TXNEG5 TXCLK5 RXNEG5 RXPOS5 LOS5 GND LOSSEL VCC LOS2 RXPOS2 RXNEG2 TXCLK2 TXNEG2 TXPOS2 RXNEG3 RXPOS3 LOS3 TXPOS3 TXNEG3 100 1 25 26
Rev. 1.11 3
RXPOS1 RXNEG1 VCC LOS7 RXPOS7 RXNEG7 RTIP1 RRING1 VCC GND VCC RRING2 RTIP2 GND TTIP2 VCC TRING2 GND TRING3 VCC TTIP3 GND RTIP3 RRING3 TXCLK3
100 LEAD THIN QUAD FLAT PACK (14 x 14 x 1.4 mm, TQFP)
XRT5897
PIN DESCRIPTION
Pin # 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 Symbol RXPOS1 RXNEG1 VCC LOS7 RXPOS7 RXNEG7 RTIP1 RRING1 VCC GND VCC RRING2 RTIP2 GND TTIP2 VCC TRING2 GND TRING3 VCC TTIP3 GND RTIP3 RRING3 TXCLK3 TXNEG3 TXPOS3 LOS3 RXPOS3 RXNEG3 TXPOS2 TXNEG2 TXCLK2 RXNEG2 RXPOS2 I I I I I O O O I I I O O O O O O I I O O O I I Type O O Description Receiver 1 Positive Data Out. Positive RZ data output for channel 1. Receiver 1 Negative Data Out. Negative RZ data output for channel 1. Positive Supply (+3.3V + 5%). Digital circuitry. Receiver 7 Loss of Signal. Asserted during LOS condition. Receiver 7 positive Data Out. Positive RZ data output for channel 7. Receiver 7 Negative Data Out. Negative RZ data output for channel 7. Receiver 1 Positive Bipolar Input. Receiver 1 Negative Bipolar Input. Positive Supply (+3.3V + 5%). Analog circuitry. Analog Ground. Positive Supply (+3.3V + 5%). Receivers 1, 2, 3, and 7. Receiver 2 Negative Bipolar Input. Receiver 2 Positive Bipolar Input. Analog Ground. Receivers 1, 2, 3, and 7. Transmitter 2 Positive Bipolar Output. Positive Supply (+3.3V + 5%). Transmitter channel 2. Transmitter 2 Negative Bipolar Output. Digital Ground. Transmitter channel 2. Transmitter 3 Negative Bipolar Output. Positive Supply (+3.3V + 5%). Transmitter channel 3. Transmitter 3 Positive Bipolar Output. Digital Ground. Transmitter channel 3. Receiver 3 Positive Bipolar Input. Receiver 3 Negative Bipolar Input. Transmitter 3 Clock Input. Use for clocked mode with NRZ data.1 Transmitter 3 Negative Data Input. Negative NRZ or RZ data input.1 Transmitter 3 Positive Data Input. Positive NRZ or RZ data input.1 Receiver 3 Loss of Signal. Asserted during LOS condition. Receiver 3 Positive Data Out. Positive RZ data output for channel 3. Receiver 3 Negative Data Out. Negative RZ data output for channel 3. Transmitter 2 Positive Data Input. Positive NRZ or RZ data input.1 Transmitter 2 Negative Data Input. Negative NRZ or RZ data input.1 Transmitter 2 Clock Input. Use for clocked mode with NRZ data.1 Receiver 2 Negative Data Out. Negative RZ data output for channel 2. Receiver 2 Positive Data Out. Positive RZ data output for channel 2.
Note: 1 Has internal pull-up 50KW resistor. Rev. 1.11 4
XRT5897
PIN DESCRIPTION (CONT'D)
Pin # 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 Symbol LOS2 VCC LOSSEL GND LOS5 RXPOS5 RXNEG5 TXCLK5 TXNEG5 TXPOS5 RXNEG4 RXPOS4 LOS4 TXPOS4 TXNEG4 TXCLK4 RRING4 RTIP4 GND TTIP4 VCC TRING4 GND TRING5 VCC TTIP5 GND RTIP5 RRING5 VCC GND VCC RRING7 RTIP7 RRING6 I I I I I O O O O O O O I I I O O O I I I I I I Type O Description Receiver 2 Loss of Signal. Asserted during LOS condition. Digital Supply (+3.3V + 5%). Digital circuitry. Loss of Signal Delay Select. "Hi" selects G.775, "Lo" selects user programmable.1 Digital Ground. Receiver 5 Loss of Signal. Asserted during LOS condition. Receiver 5 Positive Data Out. Positive RZ data output for channel 5. Receiver 5 Negative Data Out. Negative RZ data output for channel 5. Transmitter 5 Clock Input. Use for clocked mode with NRZ data.1 Transmitter 5 Negative Data Input. Negative NRZ or RZ data input.1 Transmitter 5 Positive Data Input. Positive NRZ or RZ data input.1 Receiver 4 Negative Data Out. Negative RZ data output for channel 4. Receiver 4 Positive Data Out. Positive RZ data output for channel 4. Receiver 4 Loss of Signal. Asserted during LOS condition. Transmitter 4 Positive Data Input. Positive NRZ or RZ data input.1 Transmitter 4 Negative Data Input. Negative NRZ or RZ data input.1 Transmitter 4 Clock Input. Use for clocked mode with NRZ data.1 Receiver 4 Negative Bipolar Input. Receiver 4 Positive Bipolar Input. Analog Ground. Transmitter 4 Positive Bipolar Output. Positive Supply (+3.3V + 5%). Transmitter channel 4. Transmitter 4 Negative Bipolar Output. Digital Ground. Transmitter channel 4. Transmitter 5 Negative Bipolar Output. Positive Supply (+3.3V + 5%). Transmitter channel 5. Transmitter 5 Positive Bipolar Output. Digital Ground. Transmitter channel 5. Receiver 5 Positive Bipolar Input. Receiver 5 Negative Bipolar Input. Positive Supply (+3.3V + 5%). Low level transmitter analog circuitry. Analog Ground. Low level transmitter analog circuitry. Positive Supply (+3.3V + 5%). Receiver channels 4, 5, and 6. Receiver 7 Negative Bipolar Input. Receiver 7 Positive Bipolar Input. Receiver 6 Negative Bipolar Input.
Note: 1 Has internal pull-up 50KW resistor. Rev. 1.11 5
XRT5897
PIN DESCRIPTION (CONT'D)
Pin # 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 Symbol RTIP6 GND LOSCNT RXNEG6 RXPOS6 LOS6 TXPOS6 TXNEG6 TXCLK6 GND TTIP6 VCC TRING6 GND TXPOS7 TXNEG7 TXCLK7 GND TTIP7 VCC TRING7 GND TRING1 VCC TTIP1 GND TXCLK1 TXNEG1 TXPOS1 LOS1 I I I O O O O O I I I O O I O O O I I I Type I Description Receiver 6 Positive Bipolar Input. Analog Ground. Receiver channels 4, 5, and 6. Loss of Signal Timing Clock Input. For user-programmable LOS delay.1 Receiver 6 Negative Data Out. Negative RZ data output for channel 6. Receiver 6 Positive Data Out. Positive RZ data output for channel 6. Receiver 6 Loss of Signal. Asserted during LOS condition. Transmitter 6 Positive Data Input. Positive NRZ or RZ data input.1 Transmitter 6 Negative Data Input. Negative NRZ or RZ data input.1 Transmitter 6 Clock Input. Use for clocked mode with NRZ data.1 Digital Ground. Transmitter channel 6. Transmitter 6 Positive Bipolar Output. Positive Supply (+3.3V + 5%). Transmitter channel 6. Transmitter 6 Negative Bipolar Output. Digital Ground. Transmitter 7 Positive Data Input. Positive NRZ or RZ data input.1 Transmitter 7 Negative Data Input. Negative NRZ or RZ data input.1 Transmitter 7 Clock Input. Use for clocked mode with NRZ data.1 Analog Ground. Transmitter 7 Positive Bipolar Output. Positive Supply (+3.3V + 5%). Transmitter channel 7. Transmitter 7 Negative Bipolar Output. Digital Ground. Transmitter channel 7. Transmitter 1 Negative Bipolar Output. Positive Supply (+3.3V + 5%). Transmitter channel 1. Transmitter 1 Positive Bipolar Output. Digital Ground. Transmitter channel 1. Transmitter 1 Clock Input. Use for clocked mode with NRZ data.1 Transmitter 1 Negative Data Input. Negative NRZ or RZ data input.1 Transmitter 1 Positive Data Input. Positive NRZ or RZ data input.1 Receiver 1 Loss of Signal. Asserted during LOS condition.
Note: 1 Has internal pull-up 50KW resistor.
Rev. 1.11 6
XRT5897
Test Conditions: VCC = 3.3V + 5%, TA = -40 to 25 to 75C, Unless Otherwise Specified
Symbol Parameters VCC Inputs VIH VIL Outputs VOH VOL RXCL Output High Level Output Low Level Allowable Cable Loss 0 2.4 0.4 12 V V dB IOH = -4mA IOL = 4mA Cable loss at 1.024MHz (Relative to 0dB = 2.37Vp measured from RTIP or RRING to ground). With 6dB cable loss % of peak input voltage at -3dB cable loss Relative to 0dB = 2.37Vp Measured from RTIP or RRING to ground. Relative to 0dB = 2.37Vp measured from RTIP or RRING to ground. For LOS output state change Up to 3.072MHz (Measured from RTIP or RRING to ground). Input High Level Input Low Level 2.0 5.0 0.8 V V Voltage Supply 3.135 3.3 3.465 V 3.3V operation Parameter Min. Typ. Max. Unit Conditions
ELECTRICAL CHARACTERISTICS
DC Electrical Characteristics
Receiver Specifications
RXIM RXXI RXLOSSET
Interference Margin Receiver Slicing Threshold LOS Must Be Set If RX Sig. Atten. 32dB (For Any Valid Data Pattern) LOS Must Be Cleared If RX Sig. Atten. < 9dB Hysteresis on Input Data Input Impedance Jitter Tolerance: 20Hz 700Hz 10kHz -- 100kHz Return Loss: 51khz -- 102kHz 102kHz -- 2048kHz 2048kHz -- 3072kHz
-15 45
-12 50 15 55
dB % dB
RXLOSCLR
13
dB
RXLOSHYST RXIN
2 5
dB kW
10 5 0.3 14 20 16 715 117 1260 880 920 155 1465 1065
UIpp UIpp UIpp dB dB dB mW mW mW mW All 1's Transmit and Receive 75W All Drivers Power Down All 1's Transmit and Receive 50% data density, Transmit and Receive Per ITU--T G.703
Power Specifications VCC = 3.3V PD PD PC PC Power Dissipation Power Dissipation Power Consumption 75W Power Consumption 75W
Rev. 1.11 7
XRT5897
PC PC Power Consumption 120W Power Consumption 120W 1025 745 1255 945 mW mW All 1's Transmit and Receive 50% data density, Transmit and Receive
Note: Bold face parameters are covered by production test and guaranteed over operating temperature range.
Rev. 1.11 8
XRT5897
ELECTRICAL CHARACTERISTICS (CONT'D) Test Conditions: VCC = 3.3V + 5%, TA = -40 to 25 to 75C, Unless Otherwise Specified
Symbol VTXOUT VTXOUT TXPW PNIMP T1 T2 TSU THO TR TF T3-noclk T3-clk T4 T5 T6 T7 Parameter Output Pulse Amplitude (RL = 75W) Output Pulse Amplitude (RL = 120W) Output Pulse Width Pos/Neg Pulse Unbalanced TXCLK Clock Period (E1) TXCLK Duty Cycle Data Set-up Time, TDATA to TXCLK Data Hold Time, TDATA to TXCLK TXCLK Rise Time (10% to 90%) TXCLK Fall Time (10% to 90%) Data Prop. Delay No-Clock Mode Data Prop. Delay Clock Mode Receive Data High RX Data Prop. Delay Receive Rise Time Receive Rise Time 219 30 75 30 40 40 35 470 244 269 40 40 40 50 Min. 2.13 2.70 224 Typ. 2.37 3.0 244 5 488 50 70 Max. 2.60 3.30 264 Unit V V ns % ns % ns ns ns ns ns ns ns ns ns ns 50% TXCLK Duty Cycle 0dB Cable Loss 15pF Load 15pF Load 15pF Load 50% TXCLK Duty Cycle 50% TXCLK Duty Cycle Conditions Trans. = 1:2 ratio, 9.1W in series with each end of primary Trans. = 1:2 ratio, 9.1W in series with each end of primary AC Electrical Characteristics
Note: Bold face parameters are covered by production test and guaranteed over operating temperature range.
ABSOLUTE MAXIMUM RATINGS Storage Temperature . . . . . . . . . . . . -65C to +150C Operating Temperature . . . . . . . . . . -40C to +75C Supply Voltage . . . . . . . . . . . . . . . . . . +0.3V to +6.0V
Rev. 1.11 9
XRT5897
Disabling Output Drivers Output drivers may be individually disabled (hi-z output) by either of the following methods. 1. Either connect the transmit data inputs TXPOS and TXNEG for the channel to be disabled to a logic 1 source (VCC), or allow them to float (inputs have internal pull--up resistors). TRANSFORMER REQUIREMENTS
Turns Ratio 1:2 CT Line Impedance 75W or 120W Turns Ratio 1:2 Line Impedance 75W or 120W
2. Connect TXCLK for the channel to be disabled to logic 0 source (Ground), and also apply data to the TXPOS and TXNEG inputs of that channel.
Table 1. Input Transformer Requirements
Table 2. Output Transformer Requirements
Note: The same type 1:2 CT ratio device may be used at both receiver input and transmitter output.
The following transformers have been tested with the XRT5897: HALO type TG26-1205(package contains two 1 CT:2 CT ratio transformers) Pulse type PE-65535 (1:2 CT ratio) Transpower Technologies type TTI 7154-R (1:2 CT ratio)
Magnetic Supplier Information: HALO Electronics, Inc. P.O. Box 5826 Redwood City, CA 94063 Tel. (415) 568-5800 Fax. (415)568-6161 Pulse Telecom Product Group P.O. Box 12235 San Diego, CA 92112 Tel. (619) 674-8100 Fax. (619) 674-8262 Transpower Technologies, Inc. 24 Highway 28, Suite 202 Crystal Bay, NV 89402--0187 Tel. (702) 831--0140 Fax. (702) 831--3521
Rev. 1.11 10
XRT5897
TSU
THO
TXPOS (n) TSU THO
TXNEG (n) T2 TXCLK (n)
T1
TR
TF
TXPW T3 T3 VTXOUT VTXOUT TXPW
TXOUT (n)
Figure 2. Transmit Timing Diagram
RXIN (n) T5
T4
T6
T7
RPOS (n) T5 T4 T6 T7
RXNEG (n)
Figure 3. Receive Timing Diagram
Rev. 1.11 11
XRT5897
RETURN LOSS SPECIFICATIONS The following transmitter and receiver return loss specifications are based on a typical 1:2CT ratio transformer.
75W Frequency Range 51kHz to 102kHz 102kHz to 2.048MHz 2.048MHz to 3.072MHz Min. 16 16 11 Typ. 22 22 18 Min. 10 10 10 120W Typ. 15 15 14 Unit dB dB dB
Table 3. Transmitter Return Loss Specification Transmit Return Loss Notes D Output transformer ratio is 1:2 (return loss exceeds ETSI 300 166 with this transformer). D For both 75W and 120W applications, 9.1W, 1% resistors are connected between each end of the transformer primary and the XRT5897 TTIP and TRING pins.
120W Typ. 28 34 26 Min. 15 22 20 Typ. 18 25 30 Unit dB dB dB
75W Frequency Range 51kHz to 102kHz 102kHz to 2.048MHz 2.048MHz to 3.072MHz Min. 16 22 18
Table 4. Receiver Return Loss Specification Receiver Return Loss Notes D Input transformer ratio is 1:2 CT. D Transformer center tap is grounded. D Each half of transformer secondary is terminated with 150W for 75W operation, or 240W for 120W operation (resistors are 1% tolerance).
Rev. 1.11 12
XRT5897
SYSTEM DESCRIPTION This device is a seven channel E1 transceiver that provides an electrical interface for 2.048Mbps applications. Its unique architecture includes seven receiver circuits that convert ITU G.703 compliant bipolar signals to TTL compatible logic levels. Each receiver includes a LOS (Loss of Signal) detection circuit that may be configured for either a fixed or a user-programmable LOS response time delay. Similarly, in the transmit direction, seven transmitters convert TTL compatible logic levels to G.703 compatible bipolar signals. Each transmitter may be operated either with RZ, or NRZ data types. In NRZ mode a transmit clock is required as well. The following description applies to any of the seven receivers or transmitters contained in the XRT5897. Therefore, the suffix numbers for a particular channel are deleted for simplicity. i.e. "RTIP" applies to RTIP1 through RTIP7. Receiver Operation A bipolar signal is transformer-coupled to the receiver differential inputs (RTIP and RRING). The receiver is able to tolerate up to 12dB of line loss measured at 1.024MHz. It contains slicing circuitry that automatically samples the incoming data at a fixed percentage (50% nominal) of the peak signal amplitude. A precision peak detector maintains the slicing level accuracy. The TTL compatible receiver output data rails appear at the RXPOS and RXNEG pins. The pulse width of this data; which is in RZ format, is a function of the amount of the cable loss present. Receiver Loss Of Signal Detection (LOS) Absence of signal at any receiver input is detected by the loss of signal (LOS) circuit. One LOS detection circuitry is provisioned for each receiver. The LOS signal is asserted (LOS=1) when a LOS condition is detected and is cleared (LOS=0) when a valid input signal is restored. Two modes of LOS circuit operation are supported. These distinct modes are called "automatic" and "user-programmable". When LOSSEL (pin 38) is set to logic "1", the automatic mode is selected. In this mode the LOS condition will be declared and cleared in full compliance with ITU G.775 specification. When LOSSEL is connected to logic "0", the user-programmable delay mode is enabled. In this mode the user has the option of extending the delay of LOS declaration and clearing specified in the ITU G.775. This is done by providing a user-supplied clock to LOSCNT (pin 73). The "user programmable mode" is provisioned to allow systems designers to comply with older versions of LOS specifications in legacy systems. It needs to be stressed that the delay for declaration and clearing of the LOS condition will never be less than the range specified in the G.775 specification (10-255 pulse intervals). The LOS detection/clearing circuitry of the XRT5897 in "automatic" mode will detect LOS when the incoming signal has "no transitions," i.e. when the signal level is less than or equal to a signal level AD dB below nominal signal level, for N consecutive pulse intervals, where 10Rev. 1.11 13
XRT5897
Transmitters This device contains four identical ITU G.703 compliant transmitters. The output stage of each transmitter is a differential voltage driver. External resistors need to be connected to the primary of output transformer. This is necessary to maintain an accurate source impedance that ensures compliance to ETSI 300 166 return loss requirement. TTL compatible dual rail transmit data signals are supplied to TXPOS and TXNEG inputs. The transmitter differential outputs TTIP and TRING are connected to the output transformer primary through series 9.1W resistors. All the four transmitters can be operated in two distinct modes of operation referred to as "clocked" or "clockless" modes. The operational mode is selected automatically based on the signal provided to TXCLK input. If a clock is present at this pin, the transmitter detects its presence and operates in the clocked mode. In this mode, the transmit input should be supplied with full-width NRZ pulses. If a clock is not present at the TXCLK input (pin is left open), the part operates in the clockless mode. In this mode, RZ data should be supplied to the device. Each transmit channel of XRT5897 has a duty cycle correction circuitry. This enables the device to produce output bipolar pulses fully compliant with G.703 despite having TXCLK signal with 30% to 70% duty cycle.
269 ns (244 + 25) 20% V = 100% 10% 10% 20% 194 ns (244 -- 50) Nominal pulse
50% 244 ns 219 ns (244 -- 25)
10% 0% 10% 20%
10% 10%
488 ns (244 + 244)
Note: V corresponds to the nominal peak value
Figure 4. CCITT G.703 Pulse Template
Rev. 1.11 14
XRT5897
Transmitter Output Pulse Measurement Figure 1 shows a typical transmit pulse plotted on the template shown in ITU G.703 Figure 15/G.703. The following conditions apply: VCC=3.30V Transmitter output transformer secondary terminated with 120W. All ones signal. Receiver output looped backed into transmitter digital input. Operation without transmitter clock (RZ data). Measurement made with a Tektronix TDS640 digital scope set to full bandwidth.
1.2
1.0
0.8 Normalized Amplitude
0.6
0.4
0.2
0
-0.2 -244 -122 0 Time (ns) 122 244
Figure 5. XRT5897 Output Pulse
Rev. 1.11 15
XRT5897
Transmitter Output Return Loss Measurements The following measurements were made with a Wandel and Goltermann SNA--2 Network Analyzer equipped with an RFZ--1 75W Return Loss Bridge. A 75W to 120W impedance matching transformer was used to make the 120W measurement. A network analyzer calibration run subtracted out the effects of this transformer. Test Conditions: D Output transformer ratio was 1:2. D Transmitter series resistors (R3 and R4 in Figure 1) were 9.1W. D Device was powered from a 3.3V source, transmitter was enabled, and no output data was present. This configuration was used for both 75W and 120W measurements. The only change was the termination resistance provided by the return loss bridge.
Test Results: Table 5 compares measured output return loss with requirements in ETSI FINAL DRAFT prETS 300 166, June 1993. These results show that measured return loss is mainly determined by the characteristics of the output transformer. This is particularly evident for the 120W load where the measured result is better than the calculated value.
Specified Frequency 0.025 fb 0.05 fb 1.5 fb
Frequency (KHz) 51.2 102.4 3072
ETSI Spec. (Min. dB) 6 8 8
Meas. Value (dB) 75W Load 22.6 22.6 18.0
Meas. Value (dB) 120W Load 15.4 15.7 14.6
Table 5. Transmitter Output Return Loss Measurements
Notes: fb = 2048KHz This data shows that the XRT5897 is fully compliant with the ETSI Output Return Loss Specification for E1 operation with either 75W or 120W loads.
Rev. 1.11 16
XRT5897
The following pictures show typical results of measurements that made over a 50 KHz to 3.5MHz frequency range.
Figure 6. 75W Return Loss Measurement
Figure 6, shows a return loss better than 20dB at low frequencies that decreases to about 12dB at 3.5MHz. Since the source and load resistances are well--matched, the return loss degradation is due to the transformer.
Figure 7. 120W Return Loss Measurement Figure 7, shows that for the 120W case, transformer characteristics improve return loss at lower frequencies. At 3.5 MHz, return loss is close to the calculated 13.8dB for a 75W source terminated with 120W.
Rev. 1.11 17
XRT5897
Output Transformer Selection A 1:2 ratio transformer is recommended for both 75W and 120W operation because the transmitter, when equipped with this device, meets both the ITU G.703 output pulse amplitude requirement and, the ETSI return loss specification. Although a center--tapped output transformer is not required, choosing a part with a center-tapped secondary allows the use of the same type of unit at the receiver input. A theoretical justification for the 1:2 ratio transformer follows:
RSpos VSpos VSneg
TTIP
R3 1:n VO RL
TRING RSneg R4
Figure 8. Transmitter Line Driver Model Where: Vspos = Vsneg = 1.25V typical (Differential line driver peak output voltage swing) Rspos = Rsneg = 0.8W typical (Differential line driver internal source resistance) R3 = R4 = 9.1W (Differential line driver external source resistance from Figure 1) RL = 75W or 120W (Transmitter load resistance) n = 2 (Transformer turns ratio) Vo = Transmitter peak output voltage (Measured across RL = 75W or RL = 120W) Figure 9 may be converted to a single--ended model:
RSint RSext 1:n VS VO RL
Figure 9. Single-ended Line Driver Model Where: VS = /Vspos/ + /Vsneg/ RSint = RSpos + Rsneg RSext = R3 + R4
Rev. 1.11 18
XRT5897
This may be further simplified:
RT
Vs
I
Veq
Figure 10. Equivalent Circuit
Where: RT = RSint + Rsext Req = Therefore: I= Vs RT + Req RL n2
Veq = I Req Vo = n Veq And: Return Loss = 20 log RT + Req RT-- Req
Table 6. contains the results of calculations made with these equations. The numbers show that output pulse amplitude is within millivolts of the nominal values of 2.37V and 3.00V specified by ITU G.703 for 75W and 120W operation. Also, the 1:2 ratio transformer provides an almost-perfect match for 75W operation, and return loss is well within the ETSI specification for the 120W load.
Load Resistance RL (W) 75 120
Pulse Amplitude Vo (Volts Peak) 2.43 3.01
Output Return Loss (dB) 31.3 13.8
Table 6. Calculated Transmitter Pulse Amplitude and Return Loss
Rev. 1.11 19
XRT5897
100 LEAD THIN QUAD FLAT PACK (14 x 14 x 1.4 mm, TQFP)
Rev. 2.00
D D1 75 51
76
50
D1
D
100
26
1 A2 A Seating Plane A1 B
25
e
C
a
L
INCHES SYMBOL A A1 A2 B C D D1 e L MIN MAX
MILLIMETERS MIN 1.40 0.05 1.35 0.17 0.09 15.80 13.90 MAX
0.055 0.063 0.002 0.006 0.053 0.057 0.007 0.011 0.004 0.008 0.622 0.638 0.547 0.555 0.020 BSC 0.018 0.030 0 7
1.60 0.15 1.45 0.27 0.20 16.20 14.10 0.50 BSC 0.45 0.75 0 7
a
Note: The control dimension is the millimeter column
Rev. 1.11 20
XRT5897
NOTICE EXAR Corporation reserves the right to make changes to the products contained in this publication in order to improve design, performance or reliability. EXAR Corporation assumes no responsibility for the use of any circuits described herein, conveys no license under any patent or other right, and makes no representation that the circuits are free of patent infringement. Charts and schedules contained herein are only for illustration purposes and may vary depending upon a user's specific application. While the information in this publication has been carefully checked; no responsibility, however, is assumed for inaccuracies. EXAR Corporation does not recommend the use of any of its products in life support applications where the failure or malfunction of the product can reasonably be expected to cause failure of the life support system or to significantly affect its safety or effectiveness. Products are not authorized for use in such applications unless EXAR Corporation receives, in writing, assurances to its satisfaction that: (a) the risk of injury or damage has been minimized; (b) the user assumes all such risks; (c) potential liability of EXAR Corporation is adequately protected under the circumstances. Copyright 2001 EXAR Corporation Datasheet October 2001 Reproduction, in part or whole, without the prior written consent of EXAR Corporation is prohibited.
Rev. 1.11 21

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